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The re-entrant structures are among the simple unit cell designs that have been widely used in the design of mechanical metamaterials. Changing the geometrical parameters of these unit cell structures, their overall elastic properties (i.e., elastic stiffness and Poisson’s ratio), can be simultaneously tuned. Therefore, different design strategies (e.g., functional gradient) can be implemented to design advanced engineering materials with unusual properties. Here, using the theory of elasticity and finite element modeling, we propose a fast and direct approach to effectively design the microarchitectures of mechanical metamaterials with re-entrant structures that allow predicting complex deformation shapes under uniaxial tensile loading. We also analyze the efficiency of this method by back calculating the microarchitectural designs of mechanical metamaterials to predict the complex 1-D external contour of objects (e.g., vase and foot). The proposed approach has several applications in creating programmable mechanical metamaterials with shape matching properties for exoskeletal and soft robotic devices.

Magnetorheological elastomers (MREs) are polymers reinforced by ferromagnetic particles that show magnetic dependent behavior. Mixing MREs with reinforcing fibers can create a new class of material so-called “MRE composites, MRECs” with additional functionalities and properties. Here, using a Generalized Maxwell model, we proposed a new magnetic-dependent rheological model by considering the hysteresis phenomenon for MREs to predict the dynamic damping responses of MREC plates reinforced by fibers in the frequency domain. We also investigated the influence of magnetic flux intensity, the volume fraction of the fiber, the orientation angle of the fibers, the number of layers, as well as the fiber-to-matrix stiffness ratio on the natural frequency, loss factor, and mode shapes of MRECs plates. Our results suggest that homogenously increasing the elastic properties of the MRECs through the spatial distribution of fibers and changing the fiber-to-matrix stiffness ratio can effectively tailor the dynamic properties of MRECs. Tailoring these properties can provide additional freedom for the fabrication of 4D-printed MRE-based composites.

Dendrimers are symmetric, round and ramose macromolecules made up of monomers which have a certain structural order. The aim of this study was to evaluate the antibacterial effects of different concentrations of G3-poly-amidoamine dendrimer (G3-PAD) on 7 species of gram-negative and gram-positive bacteria in aqueous solutions. Different concentrations of G3-PAD were prepared and from each bacterial species, a suspension with a different pH was prepared according to the McFarland 0.5 standard. Bacteria were left in a 37 degrees C incubator and shaker from 0 to 60 min, and were cultivated on a Mueller-Hinton Agar plate. The bacteria that grew on each plate were counted and analyzed. The results showed that the antibacterial effect of G3-PAD in aqueous solutions was directly related to dendrimer concentration, contact time and pH. The strongest effect on Salmonella and Bacillus Subtilis was at pH = 6.5 and 7.5 and contact time 45 min, and in pH = 9, contact time 30 min; for Enterococcus faecalis in all three pH, it was 60 min; for Staphylococcus Aureus in pH = 6.5 and 7.5, 60 min and in pH = 9, 30 min; for E. coli in pH = 6.5 and 7.5, 60 min and in pH = 9, 45 min. G3-PAD showed its strongest effect on Shigella bacteria in pH = 6.5, contact time 60 min. In pH = 7.5 there was no optimum condition and in pH = 9, the optimum contact time was 60 min. The strongest effect of G3-PAD on all species was seen in 2000 ppm concentration. These results show a new strategy to improve bacteria elimination from aqueous solutions. However, safely using dendrimers for disinfecting drinking water still needs more research.

Background & Aims of the Study: The most important compounds in hospital wastewater are antibiotics, disinfectants, anesthetics, radioactive elements, static cytotoxic agents, other chemicals and hazardous materials that caused to be different domestic sewage. The purpose of this study was the evaluation of performance of extended aeration biological system in pollutants removal from Razi Hospital wastewater treatment plant (WTP), Ahvaz city of Iran. Materials and Methods: The hospital wastewater disposal and treatment in Razi hospital have been studied in this cross-sectional research. Total of 12 samples from effluents of wastewater treatment plants were collected and tested for pH, Biological Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Total Suspended Solid (TSS) and Total Coliform (TC). EPA standard method was used for conducted trials. Finally, the relationship between results at different months and stations was done, using SPSS18 and descriptive statistics. Results: Results shown that parameters average in effluent was pH=7.46، BOD= 48.58 mg/l, COD=99.25 mg/l, TSS=54 mg/l, NH3=5.65mg/l, Turbidity=29.57 NTU. Also total coliform and fecal coliform of effluent were 46.19 MPN/100 ml and 36.65 MPN/100 ml, respectively. According to results, the percentage of BOD, COD, TSS and TC removal in WTP were 85.21, 82.46, 86 and 90.15. Conclusion: Based on these findings, Razi hospital effluent wastewater treatment plant was mitted at Iran environmental standards for discharge to recipient wasters. Based on the result of our study, Extended Aeration Biological System is a comparatively suitable process for BOD, COD, TSS and TC removal from hospital wastewater.

In this study, the potential of hexadecyl trimethyl ammonium bromide modified montmorillonite (HDTMA-Mt) to remove the synthetic dyes Alizarin Red S (ARS) and Bromocresol Green (BCG) from aqueous media was assessed. The effect of different factors including surfactant loading rate onto the clay, contact time, pH, adsorbent dosage and dye concentrations, on the removal of ARS and BCG in batch systems were investigated. The adsorbent was characterized by means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD). The equilibrium time for ARS and BCG was reached at 40 and 20 min, respectively, under optimized conditions (i.e. pH = 3, adsorbent dosage=1 g/L, surfactant loading rate onto the clay 70% of the cation exchange capacity (CEC) for ARS and 120% of the CEC for BCG, ARS concentration 50 mg/L and BCG concentration 500 mg/L). The adsorption rate of both dyes fitted the pseudo-second-order kinetic model and the equilibrium data was described by the Freundlich isotherm equation. The maximum monolayer adsorption capacities were equal to 666.6 and 1250 mg/g for ARS and BCG, respectively. Therefore, the HDTMA-Mt can be considered as an effective adsorbent for the removal of ARS and BCG from aqueous solutions.

Recently application of functionally graded materials(FGMs) have attracted a great deal of interest. These materials are composed of various materials with different micro-structures which can vary spatially in FGMs. Such composites with varying thickness and non-uniform pressure can be used in the aerospace engineering. Therefore, analysis of such composite is of high importance in engineering problems. Thermoelastic analysis of functionally graded cylinder with variable thickness under non-uniform pressure is considered. First order shear deformation theory and total potential energy approach is applied to obtain the governing equations of non-homogeneous cylinder. Considering the inner and outer solutions, perturbation series are applied to solve the governing equations. Outer solution for out of boundaries and more sensitive variable in inner solution at the boundaries are considered. Combining of inner and outer solution for near and far points from boundaries leads to high accurate displacement field distribution. The main aim of this paper is to show the capability of matched asymptotic solution for different non-homogeneous cylinders with different shapes and different non-uniform pressures. The results can be used to design the optimum thickness of the cylinder and also some properties such as high temperature residence by applying non-homogeneous material.

The present paper develops piezo-thermo-elastic analysis of a thick spherical shell for generalized functionally graded piezoelectric material. The assumed structure is loaded under thermal, electrical and mechanical loads. The mechanical, thermal and electrical properties are graded along the radial direction based on a power function with three different non homogenous indexes. Primarily, the non homogenous heat transfer equation is solved by applying the general boundary conditions, individually. Substitution of stress, strain, electrical displacement and material properties in equilibrium and Maxwell equations present two non homogenous differential equation of order two. The main objective of the present study is to improve the relations between mechanical and electrical loads in hollow spherical shells especially for functionally graded piezoelectric materials. The obtained results can evaluate the effect of every non homogenous parameter on the mechanical and electrical components.

An impact behavior of striker on double-layered (DLGS) and multi-layered (MLGS) graphene sheet is investigated based on three degrees of freedom spring-mass model and the molecular dynamics (MD) simulations. The van der Waals (vdW) interaction between two layers of a DLGS is incorporated in the analytical model. An analytical model is able to predict the time history of deflection and vibration of the graphene sheets (GSs) and MD simulation cooperates various values of a dimension, chirality, boundary condition, number of layered and also striker parameters such as mass, velocity, and geometry. The analytical method is verified by MD simulations. The results from the spring-mass model demonstrated good agreement with MD simulation for a square and rectangular DLGS. The analytical model also accounts the relative motion between two layered of GS that is due to the local indentation in upper GS as can be seen in MD simulation. The maximum deflection and vibration after impact by the sphere, cone, sharp cone, and block strikers are investigated by MD simulations.

This paper studies Second order Shear Deformation Theory (SSDT), as a higher order shear deformation theory, for an axisymmetric functionally graded shell of revolution with variable thickness. According to symmetrical condition, there is not any displacement and any variation along the symmetric direction. The governing equations of proposed shell are derived by virtual work principle. As a special case, the governing equations are rewritten for a cylinder with variable thickness and non-uniform internal pressure. The comparison between current work, classical theory and First order Shear Deformation Theory (FSDT) are illustrated with some numerical results. Non-homogenous material, boundary condition effects, non-uniform pressure, arbitrary curvature with variable thickness and nonlinear displacement field are some advantages of current work. The optimum design of shell is the main goal of current approach that has a wide industrial application like aerospace engineering.

Elastic analysis of a functionally graded thick-walled cylindrical pressure vessel is analytically studied in the present research. Gradation is considered for all mechanical properties along the thickness direction based on a power function. The constitutive relations are developed in the general cylindrical coordinate system for an axisymmetric pressurized cylinder. For simulation of these two deformation components, first order shear deformation theory is considered. The FG cylinder is subjected to longitudinally non-uniform pressure along the length of the cylinder. The present problem is applicable for simulation of non-uniform pressurized cylinder by fluids or gases.

Background: Among ambient air pollutants, particulate matter (PM) has the most undesired adverse effects on human health. Many studies have reported that there is a strong correlation between PM concentrations and hospital admissions due to chronic or acute respiratory and cardiovascular diseases. Objectives: The aims of this study were to evaluate the relationship between air quality and health endpoints of PM 10 in Khorramabad, Iran. Materials and Methods: The PM 10 sampling was carried out with a high-volume sampler at a flow rate of 1.1 - 1.4 m 3 /min from January through December 2014. Meteorological data was also collected and evaluated. The total mortality and morbidity rates were calculated using the AirQ2.2.3 software model. Results: The highest concentrations of PM 10 were obtained in July, with the mean concentration of 136.48 µg/m 3 . Eastern and southeastern winds are the prevailing and semi-prevailing winds in Khorramabad. The worst air quality was also observed in July. The total mortality rate during the study was estimated to be 320 persons. Conclusions: In order to diminish the health impacts of particulate matter in Khorramabad, health training for the public, especially for persons with chronic lung and heart diseases, the elderly, and children, should be conducted by health systems to encourage them to reduce their activities during dusty days.

The exact thermoelastic analysis of a functionally graded piezoelectrical (FGP) rotating cylinder is investigated analytically. The cylinder is subjected to a combination of electrical, thermal, and mechanical loads simultaneously. The structure is a simplified model of a rotational sensor or actuator. The basic governing differential equation of the system is obtained by using the energy method. A novel term, named as the additional energy, is introduced to exact the evaluation of the energy functional. The solution to the governing differential equation is presented for two types of boundary conditions including free rotating and rotating cylinders exposed to the inner pressure. The effect of the angular velocity is investigated on the radial distribution of various components. The mentioned structure can be considered as a sensor for measuring the angular velocity of the cylinder subjected to the pressure and temperature. The obtained results indicate that the electrical potential is proportional to the angular velocity.

Many construction projects are carried out around the world but only some of them are completed on time. Many factors indicate the success of a project such as: completion on time, within budget, within specified quality, satisfaction of the client, and the rate of change order. Delays in a construction project can be regarded as failure. This paper aims to investigate the causes of delay in Iranian construction projects. This research was conducted by questionnaire survey to solicit the causes of delay from the viewpoints of clients, consultants, and contractors. One hundred and twenty five sets of questionnaires were distributed to the respondents. The results demonstrate that finance and payments of completed work, improper planning, site management, contract management, and lack of communication between the parties are the key reasons for delay.

Background Due to the limited fresh water resources and its important role in life and progress of nations, maintaining the water quality is necessary. Objectives The purpose of this study was to evaluate quality of Khorramrood River water using Indexes of water quality including water quality index (WQI) and Wilcox and zoning with geographical information systems (GIS). Patients and Methods In this cross-sectional study, the quality parameters required for the calculation of quality indicators, i. e. WQI and Wilcox index, were measured by using standard methods at six selected stations during six months in 2012. This Parameters consisted of pH, dissolved oxygen, total dissolved solids, electrical conductivity, biochemical oxygen demand, turbidity, temperature, phosphate, nitrate, fecal coliform, calcium, magnesium, and sodium. River zonation was done using the software GIS. Results By using WQI, the best water quality was reported in station number one with the scalar quantity of 71.11 (water with best quality) and the worst water quality was in station number six with scalar quality of 42.77 (water with bad quality). By using a Wilcox index for agricultural consumption, the river water based on EC classified in C2 and C3, and based on SAR it classified in S4. The quality parameters concerning the total dissolved solids, turbidity, nitrate, phosphate, and BOD5 in some sampling stations were higher than standard limit of surface water. Conclusions According to the average of WQI index, quality of water was good in station number one, medium in station number two, and bad in the rest of stations. According to the WILCOX Index, qualities of water in third station were medium and in the rest were good.

This paper illustrates an innovative approach to obtain an analytical model for elastic, multilayer, anisotropic, and moderately thick plates. The goals of the proposed approach are (i) provide an accurate stress description, (ii) take into account the effects of material anisotropies and inhomogeneities, and (iii) lead to a plate model that does not need shear correction factors. The first step of the modeling procedure is the weak formulation of the 3D elastic problem. In particular, we choose the Hellinger–Reissner functional expressed in a way that privileges an accurate description of stress field. The second step consists of the reduction of the 3D elastic problem weak formulation to a 2D weak formulation (i.e. the properly called plate-theory) using the dimension reduction method. Finally, the third step allows to obtain the plate-theory strong formulation. We evaluate some analytical solutions of the obtained plate-theory and we compare them with Classical Plate Theory, First order Shear Deformation Theory, and Elasticity Theory solutions with the aim to evaluate the proposed method accuracy. The results highlight the following main advantages: needless of shear correction factors and accurate description of both stress and displacement fields also in complex situations, like multilayer, anisotropic, and moderately thick plates.

Shear deformation theory is employed for electro elastic analysis of a functionally graded piezoelectric cylinder as a physical sensor for estimation and controlling the internal pressure. Except Poisson ratio, all mechanical and electrical properties are graded along the radial coordinate system. The present paper develops the previous study using the shear deformation theory as a capable and advantageous theory instead of plane elasticity theory. Two radial and axial deformations are simulated using the first order shear deformation theory. Electric potential is supposed as a quadratic function along the thickness direction and as an unknown function along the longitudinal direction. Comparison between the present results at the regions that are adequate far from two ends of the cylinder with the results of plane elasticity theory justifies accuracy and capability of the present method. Some useful graphical and numerical results are presented in this study. The discussed problem in this paper has many advantageous properties and application in measurement and controlling of the mechanical and electrical components because of using the functionally graded materials instead of an isotropic material. DOI: http://dx.doi.org/10.5755/j01.mech.18.3.1875

The present paper addresses the thermo piezo magneto elastic behavior of a functionally graded piezomagnetic cylinder under thermal, magnetic and mechanical loads. All mechanical, thermal and magnetic properties are graded in the radial direction. The cylinder is subjected to inner pressure, thermal and magnetic loads. Temperature distribution can be obtained using solution of the heat transfer equation with general boundary conditions. Employing the equilibrium relations for both mechanical and magnetic components presents two basic equations for derivation of unknown functions. After solution of the problem, the distribution of the mechanical and the magnetic components can be presented for different values of non homogenous index. The effect of non homogenous index on the mechanical and magnetic distribution presents best optimization for intelligent manufacturing and design of the materials. Used material in this paper can be considered as a sensor for determination of the physical components and as an actuator in the micro positioning. Uniform distribution of the mechanical or the magnetic components can be obtained for special value of non homogeneity. These uniform distributions have many advantageous conditions for designer and manufactures. Key words: piezomagnetic, non homogenous index, solution, root.

Maturity models are one of the widespread areas in the field of improving organizational performance. They identify organizational strengths and weaknesses as well as providing benchmarking information. There are many maturity models like OPM3, CMMI, P3M3, PRINCE, BPMM, and Kerzner's Project Management Maturity Model etc. These models are different from each other in terms of their factors and characteristics and also there is no standard related to these models. Therefore, it is important for organizations to be able to assess their situation by a comprehensive and useful model. Accordingly, the aim of this study is to compare the models and to find a suitable maturity model. This study compares recent maturity models in terms of selected variables. The result shows that OPM3 is a more suitable model than others.

In this paper, the thermopiezoelectric behavior of a thick walled cylinder with functionally graded materials is studied. The cylinder is loaded under the temperature gradient and inner and outer pressures. All the mechanical, thermal and piezoelectric properties except the Poisson ratio can be expressed as a power function in the radial direction. In the first step, with the solution of the heat transfer equation, a symmetric distribution of temperature is obtained. The stresses and electric displacement relations can be derived in terms of the temperature, electric field and strain. Substituting the resultant relations into the mechanical and electrical equilibrium equations yields the system of nonhomogeneous differential equations with two unknown variables (the mechanical displacement and the electrical potential). Solving the system of nonhomogeneous differential equations yields other mechanical and thermal terms such as the stress, displacement, electric field and electric displacement. The main result of the present study is that, by applying a proper distribution of mechanical and thermal properties in the functionally graded piezoelectric material (FGPM) solid structures, the distributions of stresses, electric potential and electric field in the FGPM can be controlled. Hence, the FGPM can be used in sensors or actuators.

The present paper deals with the analytical solution of a functionally graded piezoelectric (FGP) cylinder in the magnetic field under mechanical, thermal and electrical loads. All mechanical, thermal and electrical properties except Poisson ratio can be varied continuously and gradually along the thickness direction of the cylinder based on a power function. The cylinder is assumed to be axisymmetric. Steady state heat transfer equation is solved by considering the appropriate boundary conditions. Using Maxwell electro dynamic equation and assumed magnetic field along the axis of the cylinder, Lorentz's force due to magnetic field is evaluated for non homogenous state. This force can be employed as a body force in the equilibrium equation. Equilibrium and Maxwell equations are two fundamental equations for analysis of the problem. Comprehensive solution of Maxwell equation is considered in the present paper for general states of non homogeneity. Solution of governing equations may be obtained using solution of the characteristic equation of the system. Achieved results indicate that with increasing the non homogenous index, different mechanical and electrical components present different behaviors along the thickness direction. FGP can control the distribution of the mechanical and electrical components in various structures with good precision. For intelligent properties of functionally graded piezoelectric materials, these materials can be used as an actuator, sensor or a component of piezo motor in electromechanical systems. Piezoelectrics are new group of materials which can be used as a sensor or actuator in electromechanical systems. These materials can exchange the mechanical deformations into electric potential and conversely, the electric potential can be exchanged to mechanical deformation. Piezoelectric sensors or actuators may be designed as many structural elements such as beam, plate or cylindrical shell. Some applications of piezoelectric structures in sensor or actuator application, while the structure is subjected to magnetic field, is important for designer and engineer. Therefore it is necessary to analyze the functionally graded piezoelectric cylinders under magnetic field subjected to mechanical, thermal and electrical loads. Lim and He (2001) proposed an exact solution for a compositionally graded piezoelectric layer